1. Field of the Invention (Technical Field)
Embodiments of the present invention relate to a testing apparatus for space objects and more particularly to a multiple degree-of-freedom (DOF) gravity balanced space object testing apparatus.
2. Background
Physical simulation or testing of six degrees-of-freedom (DOFs) free-motion of an object in a partial-gravity or microgravity condition is often required for research and practice in aerospace industry. There is an increasing need for testing of six DOF free-motion objects because of increasing satellite on-orbit-service missions and orbit cleanup missions. The current techniques for simulating free-motion in space either cannot achieve full six DOFs (air-bearing based floating) or can achieve six DOFs but in a very short time period (about 10-30 seconds) and require very expensive facilities (aircraft, suborbital flight) or can achieve six DOFs but with altered dynamics properties (neutral buoyancy). Embodiments of the present invention are a simple, reliable, and low-cost solution.
Passive gravity balancing of a mechanical system or mechanism refers to the condition where no joint forces are required to keep the system or mechanism in equilibrium for all the configurations in its workspace. Basically, two approaches, namely, using counterweight or using springs, are available to achieve passive gravity balancing. However, using counterweight adds additional mass to the system resulting in larger moments and products of inertia of the system. Alternatively, gravity balancing with springs requires that the total potential energy (including both the gravitational energy and the elastic energy) of the mechanism remains constant at any configuration in its workspace. This approach keeps the mechanism balanced with a much smaller total mass. Some gravity balanced mechanisms using springs have been designed to serve as rehabilitation devices that compensate the gravity of patients' arms or legs.
Embodiments of the present invention comprise a multi-DOF passive space object test apparatus that preferably employs springs to achieve gravity balancing at each configuration within the workspace. All of the weight of the entire moving part of the test stand is self-balanced, such that no static load is exerted on the tested vehicle, allowing the object to be tested under a condition that is very similar to a microgravity condition.